I chacked out Dell's support forum and came across this thread that said the q6700 would work, stepping unknown. I placed a link to my model on my original post. Huh, I reclicked my link but it didn't work for a moment but now it does? Just look up Dell Dimension E520, as above I upgraded almost all the components and am looking to replace the CPU, should have went for the Core 2 as it was available as an upgrade when I was customizing it.http://en.community.dell.com/forums/p/19015068/19425007.aspx#19425007
It's the last post on the page.